Solid-state imaging device and manufacturing method for the same

ABSTRACT

Photoelectric converters are arranged two-dimensionally in a semiconductor substrate. A planarizing layer, a light shielding film, a further planarizing layer and condenser lenses are formed sequentially on the semiconductor substrate and the photoelectric converters. The light shielding film has apertures at positions corresponding to the photoelectric conversion devices. Multilayer interference filters that transmit either a red, green or blue wavelength component of light are disposed in the apertures.

This application is a Divisional of U.S. application Ser. No.11/330,396, filed Jan. 12, 2006, now U.S. Pat. No. 7,416,915 and isbased on application No. 2005-009619 filed in Japan on Jan. 17, 2005,the entire contents of each of which are hereby incorporated byreference.

BACKGROUND OF INVENTION

1. Field of the Invention

The present invention relates to a solid-state imaging device andmanufacturing method for the same, and in particular to a technique forpreventing color-mixing that occurs as a result of light which haspassed through a color filter being incident on the wrong lightreceiving device.

2. Related Art

Solid-state imaging devices, which are essentially the heart of digitalcameras that have become widely used in recent years, take color imagesby using color filters to separate incident light into its constituentcolors. FIG. 1 is a cross-sectional view showing a structure of asolid-state imaging device according to conventional technology.

As shown in FIG. 1, a solid-state imaging device 11 includes asemiconductor substrate 1101 which has photoelectric converters 1102formed therein. A planarizing layer 1103, a light shielding film 1104, aplanarizing layer 1105, color filters 1106, a planarizing layer 1107 andcondenser lenses 1108 are sequentially formed on the semiconductorsubstrate 1101 and the photoelectric converters 1102.

Apertures 1104 a are provided in the light shielding film 1104 such thatincident light can reach the photoelectric converters 1102. The colorfilters 1106 transmit only specific wavelengths of light as a result ofincluding organic pigment microparticles. Each color filter 1106transmits red, green or blue light per pixel (“Introduction toSolid-State Imaging Devices”, Ando and Komobuchi, Ed. Eizo Joho MediaGakkai, Nihon Riko Shuppankai, 1999, pp. 183-188).

However, given that the color filters 1106 pertaining to conventionaltechnology have film thicknesses of from 1.5 μm to 2.0 μm, incidentlight may travel an oblique path depending on an angle of incidence andbe incident on the wrong photoelectric converter 1102, wherebycolor-mixing occurs. In other words, light that passes through a givencolor filter is incident on a photoelectric converter that does notcorrespond to the given color filter, whereby an incorrect quantity ofincident light is detected.

In regard to this problem, the film thicknesses of the color filters1106 may be reduced. By reducing the film thicknesses of the colorfilters 1106, incident light will not travel an oblique path unless theangle of incidence is extremely large.

However, there is a limit to this miniaturization since the pigmentparticles which constitute the color filters 1106 have a particlediameter of 0.1 μm. For this reason, as the film thicknesses of thecolor filters 1106 are excessively reduced, the distribution of pigmentparticles ceases to be uniform, sensitivity reduction and colorirregularities occurs, and the color filters become impractical for use.

A technique for forming a color filter directly on the light shieldinglayer has also been proposed (Japanese Patent Application PublicationNo. 7-43517). FIG. 2 is a cross-sectional view showing a structure of asolid-state imaging device according to this conventional technique.

In FIG. 2, a solid-state imaging device 12 includes CCDs 1201,photodiodes 1202, pigmentation layers (color filters) 1203 and a lightshielding film layer 1204, with a planarizing resin layer 1205 on theCCDs and photodiodes. However, even with this structure it is notpossible to prevent color-mixing since the color filters remain thickenough to allow oblique light.

SUMMARY OF INVENTION

In view of the above issue, an object of the present invention is toprovide a small solid-state imaging device in which color-mixing due tooblique light does not occur, and a manufacturing method for the same.

To achieve the above object, the solid-state imaging device of thepresent invention includes a color filter that is composed of aninorganic material and operable to transmit a specific wavelengthcomponent of incident light; a light shielding film operable to shieldincident light; and a photoelectric converter operable to generate anelectrical signal according to a quantity of light transmitted by thecolor filter, the light shielding film having an aperture at a positionopposing the photoelectric converter, and the color filter beingdisposed in the aperture of the light shielding film.

It is possible to reduce a thickness of the solid-state imaging deviceif the color filter composed of inorganic material (hereinafter,“inorganic filter”) is disposed in the aperture of the light shieldingfilm. It is also possible to eliminate color-mixing due to oblique lightsince the distance between the color filter and the photoelectricconverter is reduced, as can the distance between the color filter and alens which focuses incident light onto the photoelectric converter.

Also, a film thickness of an inorganic filter can be reduced more easilythan an organic filter, and color-mixing attributable to the reductionin film thickness can be prevented. An inorganic filter is also moreheat resistant and light resistant than an organic filter. Furthermore,if an inorganic material is used, the inorganic filter can bemanufactured in the same semiconductor process as the photoelectricconverter, a wiring, etc., thereby simplifying the manufacturing processand reducing cost compared with an organic filter which requires apurpose-built manufacturing line.

In this case, the color filter may be a single-layer filter or amultilayer interference filter.

Also, in the solid-state imaging device pertaining to the presentinvention, a film thickness of the multilayer interference filter may beless than or equal to a film thickness of the light shielding film, aplanarizing layer may be laminated on the multilayer interference filterif the film thickness of the multilayer interference filter is less thanthe film thickness of the light shielding film, and a combined filmthickness of the multilayer interference filter and the planarizinglayer may be substantially equal to the film thickness of the lightshielding film.

According to this structure, it is possible to prevent color-mixing dueto oblique light since a distance between the photoelectric converterand the condenser lens which focuses incident light onto thephotoelectric converter can be reduced. Particularly, if a maximum filmthickness of the multilayer interference filter is substantially equalto the film thickness of the light shielding film, the device is evenmore effective because oblique light can be prevented while minimizingthe film thickness of the light shielding film.

In the solid-state imaging device pertaining to the present invention, acondenser lens may be formed on the multilayer interference filter, oron the planarizing layer if the planarizing layer is laminated on themultilayer interference filter. According to this structure, thedistance between the multilayer interference filter and the condenserlens is shortened, allowing the overall thickness of the solid-stateimaging device to be reduced, while enabling the elimination ofcolor-mixing resulting from oblique light.

In the solid-state imaging device pertaining to the present invention,the multilayer interference filter may be composed of a pair of λ/4multilayer films and a spacer layer sandwiched therebetween, eachmultilayer film being constituted from two types of alternatelylaminated dielectric layers that are of different materials and have asame optical thickness, and the spacer layer having a different opticalthickness from the dielectric layers constituting the λ/4 multilayerfilms; and the dielectric layers that constitute the λ/4 multilayerfilms may consist of two materials selected from the group consisting ofmonosilicon dioxide, monotitanium dioxide, ditantalum pentoxide,monozirconium dioxide, monosilicon mononitride, trisilicon tetranitride,dialuminum trioxide, monomagnesium difluoride, monohafnium trioxide andmonomagnesium dioxide. According to this structure, it is possible torealize a multilayer interference filter using an inorganic material.Conventionally, organic materials used in color filters are insufficientin terms of light resistance and heat resistance, although this problemcan be solved if an inorganic material is used.

The multilayer interference filter is constituted from λ/4 multilayerfilms that are formed by alternately laminating high refractive indexand low refractive index materials. The greater the difference inrefractive index between the materials, the larger the reflection bandcan be made. In general, high refractive index materials have a largeabsorption coefficient at short wavelengths, reducing the sensitivity ofthe solid-state imaging device.

In regard to this problem, if the dielectric layers that constitute theλ/4 multilayer films consist of monosilicon dioxide and monotitaniumdioxide, the problem of reduced sensitivity of the solid-state imagingdevice can be resolved since monotitanium dioxide, which has a highrefractive index and almost no absorption at short wavelengths, is used.Monosilicon dioxide is suitable as a low refractive index material sinceit is widely used in semiconductor processes.

The manufacturing method of a solid-state imaging device pertaining tothe present invention includes a first step of forming a multilayerinterference filter over a semiconductor substrate having photoelectricconverters arranged two-dimensionally; a second step of forming a grooveby removing the multilayer interference filter except for portionsopposing the photoelectric converters; and a third step of forming alight shielding film in the groove. Generally, it is desirable to havethe vast majority of incident light be incident on the multilayerinterference filter in a laminate direction since multilayerinterference filters only function to separate colors in the laminatedirection.

When the multilayer interference filter is disposed in the aperture ofthe light shielding film, as in the present invention, forming the lightshielding film after formation of the multilayer interference filterallows the amount of light that is incident on the multilayerinterference filter in the laminate direction to be maximized.Consequently, sensitivity of the solid-state imaging device can beimproved.

In this case, the third step may include, for example, a fourth step oflaminating a light shielding material on the remaining portion of themultilayer interference filter and the groove; a fifth step of forming,on the laminated light shielding material, a resist over the groove; asixth step of removing the laminated light shielding material; and aseventh step of removing the resist. Also, if the third step includes aneighth step of laminating a light shielding material on a remainingportion of the multilayer interference filter and the groove, and aninth step of removing the light shielding material laminated on themultilayer interference filter by oblique etching relative to a wafersurface, portions of the laminated light shielding material which are tobecome the light shielding film are not etched due to being blocked bythe multilayer interference filter. Consequently, the light shieldingfilm can be formed without formation of a resist, thereby enablingsimplification of the manufacturing process of the solid-state imagingdevice and a reduction in manufacturing cost. Note that the lightshielding material may be a metal.

A manufacturing method for a solid-state imaging device pertaining tothe present invention includes a first step of forming multilayerinterference filters on a semiconductor substrate having photoelectricconverters arranged two-dimensionally, the multilayer interferencefilters having different film thicknesses depending on a wavelength oflight to be transmitted; a second step of forming an insulation film onthe multilayer interference filters, the insulation film having a filmthickness greater than or equal to a difference in film thicknessbetween the multilayer interference filters; a third step of forminggrooves by removing the insulation film and the multilayer interferencefilters except for portions opposing the photoelectric converters; afourth step of laminating a light shielding material on the insulationfilm and the semiconductor substrate; and a fifth step of polishing thelaminated light shielding material and the insulation film until athickest portion of the multilayer interference filters is exposed. Aplurality of wafers can be polished simultaneously if a chemicalmechanical polishing method is used, thereby enabling more efficientmanufacturing of the solid-state imaging device compared to using anetching process in which each wafer must be processed individually.

Also, a condenser lens can be attached without providing a planarizinglayer on the multilayer interference filter since an upper surface ofthe multilayer interference filter is already planarized. Consequently,the manufacturing process is simplified, and manufacturing cost can bereduced. Note that the laminated light shielding material and theinsulation film may be polished using a chemical mechanical polishingmethod.

Also, if the light shielding material is one of tungsten and copper,tungsten and copper are widely used in CMP (Chemical MechanicalPolishing), and therefore are suitable as metallic materials to bepolished.

As mentioned above, the multilayer interference filter is disposed inthe aperture of the light shielding film in the present invention,thereby enabling the thickness of the solid-state imaging device to bereduced 2 μm more than conventional technology. Consequently, it ispossible to prevent color-mixing due to an increasing number of pixels,etc.

BRIEF DESCRIPTION OF DRAWINGS

These and other objects, advantages, and features of the invention willbecome apparent from the following description thereof taken inconjunction with the accompanying drawings, which illustrate a specificembodiment of the present invention.

In the drawings:

FIG. 1 is a cross-sectional view showing a structure of a solid-stateimaging device according to conventional technology;

FIG. 2 is a cross-sectional view showing a structure of a solid-stateimaging device according to another conventional technology;

FIG. 3 is a cross-sectional view showing a portion of a structure of asolid-state imaging device according to embodiment 1 of the presentinvention;

FIG. 4 are cross-sectional views showing a layer structure of multilayerinterference filters 107 r, 107 g and 107 b according to embodiment 1,where FIG. 4A shows the multilayer interference filter 107 r, FIG. 4Bshows the multilayer interference filter 107 g, and FIG. 4C shows themultilayer interference filter 107 b;

FIG. 5 is a graph showing spectral properties of the multilayerinterference filters 107 r, 107 g and 107 b according to embodiment 1 ofthe present invention;

FIG. 6 shows dimensions of a solid-state imaging device 1 according toembodiment 1 of the present invention;

FIG. 7 are cross-sectional views showing processes for manufacturing thesolid-state imaging device 1 according to embodiment 1 of the presentinvention;

FIG. 8 are cross-sectional views showing manufacturing processes of thesolid-state imaging device 1, continuing from FIG. 7, according toembodiment 1 of the present invention;

FIG. 9 is a cross-sectional view showing a constitution of a multilayerinterference filter manufactured by formation after a light shieldingfilm has been formed;

FIG. 10 are cross-sectional views showing manufacturing processes of asolid-state imaging device according to variation 1 of the presentinvention;

FIG. 11 are cross-sectional views showing manufacturing processes of asolid-state imaging device according to variation 2 of the presentinvention; and

FIG. 12 is a cross-sectional view showing a portion of a structure of asolid-state imaging device according to variation 5 of the presentinvention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

An embodiment of a solid-state imaging device and a manufacturing methodfor the same pertaining to the present invention is described below withreference to the drawings.

Embodiment 1 (1) Structure of the Solid-State Imaging Device

The following first describes a structure of the solid-state imagingdevice pertaining to the present embodiment. FIG. 3 is a cross-sectionalview showing a portion of a structure of the solid-state imaging deviceaccording to embodiment 1 of the present invention. As shown in FIG. 3,a solid-state imaging device 1 includes a semiconductor substrate 101,photoelectric converters 102, a planarizing layer 103, a light shieldinglayer 104, a planarizing layer 105 and condenser lenses 106.

The light shielding layer 104 has apertures 104 a in which multilayerinterference filters 107 r, 107 g and 107 b are disposed.

The condenser lenses 106 focus incident light onto correspondingphotoelectric converters 102. The multilayer interference filters 107 r,107 g and 107 b selectively transmit specific wavelength components ofincident light. The light shielding film 104 prevents light transmittedby the condenser lenses 106 from being incident on non-correspondingphotoelectric converter 102.

Each of the photoelectric converters 102 outputs an electrical signalaccording to a quantity of incident light. The planarizing layer 103 iscomposed of monosilicon dioxide and provides a flat upper surface forformation of the multilayer interference filters 107 r, 107 g and 107 b.The planarizing layer 105 provides a flat upper surface for arrangementof the condenser lenses 106.

(2) Structure of the Multilayer Interference Filters 107 r, 107 g and107 b

FIG. 4 are cross-sectional views showing a layer structure of multilayerinterference filters 107 r, 107 g and 107 b according to embodiment 1,where FIG. 4A shows the multilayer interference filter 107 r, FIG. 4Bshows the multilayer interference filter 107 g, and FIG. 4C shows themultilayer interference filter 107 b.

As shown in FIG. 4A, the multilayer interference layer 107 r has astructure in which monotitanium dioxide (TiO₂) layers 201 andmonosilicon dioxide (SiO₂) layers 202 are alternately laminated, with aspacer layer 203 r formed between the layers. The spacer layer 203 r iscomposed of monosilicon dioxide, and is sandwiched between monotitaniumdioxide layers 201.

The optical thicknesses of the monotitanium dioxide layers 201 and themonosilicon dioxide layers 202 are made the same. The optical thicknessfor one layer is obtained by multiplying the refractive index by thefilm thickness of the layer.

The multilayer interference filter 107 b reflects light in a wavelengthband (hereinafter, “reflection band”) whose central wavelength issubstantially equal to four times the optical thickness of themonotitanium dioxide layers 201 and the monosilicon dioxide layers 202,as well as transmits, from among the wavelengths included in thewavelength band, red light according to the optical thickness of thespacer layer 203 r. In the present embodiment, the central wavelength is530 nm, and the optical thickness of the spacer layer 203 r is 45 nm.

As shown in FIG. 4B, the multilayer interference filter 107 g alsoincludes monotitanium dioxide layers 201, monosilicon dioxide layers 202and a spacer layer 203 g. Although the multilayer interference filter107 g has the same reflection band as that of the multilayerinterference filter 107 b, the spacer layer 203 g composed ofmonotitanium dioxide has an optical thickness of 265 nm, therebytransmitting green light.

As shown in FIG. 4C, the multilayer interference filter 107 b also hasthe same reflection band as that of the multilayer interference filters107 r and 107 b, although the spacer layer 203 b composed ofmonotitanium dioxide has an optical thickness of 190 nm, therebytransmitting blue light.

The multilayer interference filters 107 r, 107 g and 107 b are composedof inorganic materials, and have total film thicknesses of 423 nm, 392nm and 526 nm respectively.

FIG. 5 is a graph showing spectral properties of the multilayerinterference filters 107 r, 107 g and 107 b. Graphs 301 to 303 in FIG. 5respectively show spectral properties of the multilayer interferencefilters 107 r, 107 g and 107 b. As seen in the graphs, incident light isseparated into the 3 primary colors red, green and blue in the presentembodiment, which enables color images to be taken.

Note that a matrix method using the Fresnel coefficient for example, maybe employed in designing the layer constitution and spectral propertiesof the multilayer interference filters.

(3) Dimensions of the Solid-State Imaging Device

The following describes the dimensions of the solid-state imaging device1. FIG. 6 shows dimensions of the solid-state imaging device 1. As shownin FIG. 6, the width of a single cell of the solid-state imaging device1 is 2.2 μm. This width can be varied depending on the number of pixelsin the solid-state imaging device 1. The planarizing layer 103, thelight shielding film 104 and the planarizing layer 105 are respectively2.0 μm, 0.5 μm and 0.6 μm in thickness. Consequently, the distance fromthe condenser lens 106 to the photoelectric converter 102 is 3.1 μm.

As previously mentioned, the film thicknesses of the color filters 1106pertaining to conventional technology are from 1.5 μm to 2.0 μm. Incontrast, the film thicknesses of the multilayer interference filters107 r, 107 g and 107 b are from 392 nm to 526 nm, which is a significantreduction. The present embodiment also allows the thickness of thesolid-state imaging device itself to be reduced about 2 μm.

Given that the multilayer interference filters 107 r, 107 g and 107 bpertaining to the present embodiment are composed of inorganic materialssuch as monotitanium dioxide and monosilicon dioxide, these multilayerinterference filters can be formed in the apertures 104 a of the lightshielding film 104. According to this structure, it is possible toreduce the distance between the photoelectric converters 102 and themultilayer interference filters 107 r, 107 g and 107 b, thereby enablingthe prevention of color-mixing due to oblique light being incident onthe photoelectric converters 102.

Given that the color filters 1106 of the solid-state imaging device 11pertaining to the previously mentioned conventional technology arecomposed of an organic material, it is not possible to form the colorfilters 1106 and condenser lenses 1108 in the same process as thephotoelectric converters 1102, the light shielding film 1104, wiring(not shown in the figure) and the like. In other words, it is necessaryfor the color filters 1106 and the condenser lenses 1102 to be formedseparately after the photoelectric converters 1102 and the like havebeen formed. On the other hand, the color filters 107 r, 107 g and 107 baccording to the present embodiment are composed of inorganic materials,thereby allowing the color filters 107 r, 107 g and 107 b to be formedin the same process as the photoelectric converters 102 and the like.Consequently, it is possible to realize high productivity and areduction in cost.

(4) Manufacturing Method of the Solid-State Imaging Device 1

The following describes the manufacturing method of the solid-stateimaging device 1, and in particular a manufacturing method of themultilayer interference filters 107 r, 107 g and 107 b, and the lightshielding film 104 which are formed on the planarizing layer 103. FIG. 7are cross-sectional views showing processes for manufacturing thesolid-state imaging device 1. FIG. 8 show processes continuing from FIG.7.

As shown in FIG. 7A, monosilicon dioxide layers 202 and monotitaniumdioxide layers 201 are alternately laminated on the planarizing layer103 using an RF (radio frequency) sputtering device. Next, a monosilicondioxide layer 501 is formed on the top monotitanium dioxide layer 201.The monosilicon dioxide layer 501 has an optical thickness of 150 nm.

A resist 502 is formed by applying a resist agent onto the monosilicondioxide layer 501, heat treating the applied resist agent (prebake),exposing the resist agent using a photolithography device such as astepper, developing the resist with an organic solvent or the like, andheat treating the developed resist (postbake). The resist 502 has athickness of 1 μm.

As shown in FIG. 7B, the monosilicon dioxide layer is removed by dryetching, except for a blue pixel region which is excluded using theresist 502. Conditions for etching are as follows: the etching gas ismonocarbon tetrafluoride (CF₄), the gas flow rate is 40 sccm, the RFpower is 200 W, and the degree of vacuum is 0.050 Torr.

Note that the monosilicon dioxide layer may be removed by a wet etchingprocess using hydrofluoric acid since monohydrogen monofluoride has highselectivity over monosilicon dioxide and monotitanium dioxide.

In this case, the hydrofluoric acid should be a mixture of hydrofluoricacid and an ammonium fluoride solution in a ratio of 1 to 4. Themonosilicon dioxide layer 501 can be etched by immersion in the abovemixed solution for approximately 5 seconds.

After etching is finished, an organic solvent or the like is used toremove the resist 502 (FIG. 7C), and a monosilicon dioxide layer 503 isformed using the RF sputtering device. The newly formed monosilicondioxide layer 503 has an optical thickness of 45 nm.

In the area where the monosilicon dioxide layer 501 remains as a resultof etching, the combined optical thickness of the previously formedmonosilicon dioxide layer 501 and the newly formed monosilicon dioxidelayer 503 is 195 nm.

Next, resists 504 are formed at a blue region and a red region in aprocess similar to the formation of the resist 502 (FIG. 7D). Areas ofthe monosilicon dioxide layer 503 not covered by the resists 504 arethen removed by an etching process.

As a result, a spacer layer 203 b with an optical thickness of 195 nm isformed in the blue region, and a spacer layer 203 r with an opticalthickness of 45 nm is formed in the red region. A spacer layer usingmonosilicon dioxide is not formed in the green region.

Furthermore, the RF sputtering device is used to laminate a monotitaniumdioxide layer 201, a monosilicon dioxide layer 202, a furthermonotitanium dioxide layer 201 and a further monosilicon dioxide layer202 on the monotitanium dioxide layer 201 and the spacer layers 203 band 203 r (FIG. 7E).

As a result, a spacer layer 203 g using monotitanium dioxide is formedin the green region. The spacer layer 203 g has an optical thickness of265 nm, which is equivalent to two times the optical thickness of themonotitanium dioxide layer 201.

Next, a light shielding film 104 for blocking oblique light is formed.Resists 601 are formed by applying a resist agent onto the monosilicondioxide layer 202, heat treating the applied resist agent (prebake),exposing the resist agent using a photolithography device such as astepper, developing the resists with an organic solvent or the like, andheat treating the developed resists (postbake). The resists 601 have athickness of 2.5 μm.

The multilayer interference filter is then removed, by dry etching, inregions where the light shielding film 104 is to be formed, therebyresulting in the formation of the multilayer interference filters 107 r,107 g and 107 b, and grooves where the light shielding film 104 is to beformed (FIG. 8A). An organic solvent is then used to remove the resists601.

Next, an aluminum layer 602 is formed on the monosilicon dioxide layer202 and the planarizing layer 103 (FIG. 8B). The aluminum layer 602 hasa thickness of 600 nm, which is roughly equal to the thicknesses of themultilayer interference filters 107 r, 107 g and 107 b. The aluminumlayer 602 includes portions which are to be the light shielding film104.

Resists 603 are then formed on the aluminum layer 602 (FIG. 8C). Theresists 603 are formed by applying a resist agent onto the aluminumlayer 602, heat treating the applied resist agent (prebake), exposingthe resist agent using a photolithography device such as a stepper,developing the resists with an organic solvent or the like, and heattreating the developed resists (postbake).

Next, a chlorinated etching gas is used in an etching process to removethe aluminum layer 602 on the multilayer interference filters 107 r, 107g and 107 b. The resists 603 are removed using an organic solvent or thelike (FIG. 8D), thereby resulting in the formation of the lightshielding film 104.

As mentioned above, in the present embodiment the light shielding film104 is formed after the formation of the multilayer interference filters107 r, 107 g and 107 b. However, a manufacturing method in which themultilayer interference filters are formed after the light shieldingfilm is also conceivable.

FIG. 9 is a cross-sectional view showing a constitution of a multilayerinterference filter manufactured by formation after a light shieldingfilm has been formed. When this manufacturing method is adopted as shownin FIG. 9, portions of the multilayer interference filter 703 which arein contact with the light shielding film 702 are formed following thecontour of the light shielding film 702.

On the other hand, the multilayer interference filters only function toseparate colors in the laminate direction. For this reason, there is areduction in the color separation function in portions that rise upalong edges of the apertures in the light shielding film 702. Thisreduction of color separation function becomes more marked as thethickness of the multilayer interference filters increases compared withthe area of the apertures, which runs contrary to the demand forminiaturization and an increase in pixels. The manufacturing methodpertaining to the present invention is effective in this context aswell.

(5) Variations

The present invention has been described based on the embodiment,although the present invention is certainly not limited to theabove-mentioned embodiment. The following variations can also bepracticed.

(1) In the above embodiment, only one manufacturing method of thesolid-state imaging device pertaining to the present invention isdescribed, although, needless to say, the present invention is notlimited as such. Alternatively, the manufacturing method may be asfollows.

FIG. 10 are cross-sectional views showing manufacturing processes of asolid-state imaging device according to variation 1. Variation 1 is thesame as described in the above embodiment up to FIGS. 7 and 8B. Afterforming an aluminum layer 602, oblique etching relative to a wafersurface is performed as shown by an arrow 801 in FIG. 10.

This type of etching enables the removal of unnecessary portions of thealuminum layer 602, while leaving the aluminum layer 602 in the groovessandwiched between the multilayer interference filters.

Consequently, it is possible to form the light shielding film 104without using resists, thereby simplifying the manufacturing process ofthe solid-state imaging device 1 and enabling a reduction inmanufacturing cost.

(2) The above embodiment describes a case in which the planarizing layeris formed on all the multilayer interference filters, although, needlessto say, the present invention is not limited as such. Alternatively, thepresent invention may be as follows.

FIG. 11 are cross-sectional views showing manufacturing processes of asolid-state imaging device according to variation 2. Note that theprocesses described in FIG. 7 are the same in this case, and theirdescription has thus been omitted. After forming the multilayerinterference filters composed of monosilicon dioxide layers 902,monotitanium dioxide layers 901, and spacer layers 903 r, 903 g and 903b, a monosilicon dioxide layer 905 is formed using the RF sputteringdevice (FIG. 11A).

This monosilicon dioxide layer 905 has an optical thickness of 195 nm.Resists 906 are further formed on the monosilicon dioxide layer 905 inregions where the light shielding film will not be formed. Next, groovesare formed between multilayer interference filters 908 r, 908 g and 908b using an etching process (FIG. 11B). The resists 906 are then removedusing an organic solvent or the like.

Next, a tungsten layer 910 is formed on the monosilicon dioxide layer905 and the planarizing layer 904 using a CVD (Chemical VaporDeposition) method. The tungsten layer 910 has a thickness of 600 nm(FIG. 11C).

The tungsten layer 910 and the monosilicon dioxide layer 905 arepolished using, for example, a CMP method (FIG. 11D). Upper portions ofthe multilayer interference filters 908 r, 908 g and 908 b areplanarized as a result, and formation of the light shielding film iscompleted.

Lastly, the solid-state imaging device is completed by fitting condenserlenses 909 on the multilayer interference filter 908 b and the tungstenlayer 910.

According to this structure, the light shielding film can be formedusing only the CMP method without undergoing an etching process. Themanufacturing process of the solid-state imaging device can also besimplified since the upper surface of the solid-state imaging device isplanarized at the same time as the light shielding film is formed.

(3) The above embodiment describes a case in which the multilayerinterference filters have five layers or seven layers, although,needless to say, the present invention is not limited as such.Alternatively, the multilayer interference filters may have four or lesslayers, six layers, or eight or more layers.

In the above embodiment, the number of layers in the multilayer filmswhich sandwich the spacer layers is identical (vertically symmetric),although this is not a requirement. It is possible to obtain the effectsof the present invention regardless of the number of layers in themultilayer interference filters.

(4) The above embodiment describes a case in which the materialscomposing the multilayer interference filters are monosilicon dioxideand monotitanium dioxide, although, needless to say, the presentinvention is not limited as such. Alternatively, ditantalum pentoxide(Ta₂O₅), monozirconium dioxide (ZrO₂), monosilicon mononitride (SiN),trisilicon tetranitride (Si₃N₄), dialuminum trioxide (Al₂O₃),monomagnesium difluoride (MgF₂), monohafnium trioxide (HfO₃) ormonomagnesium dioxide (MgO₂) may be used.

Irrespective of the material used, the present invention has the sameeffects of suppressing color-mixing that comes with miniaturization ofsolid-state imaging devices and suppressing the reduction of the colorseparation function.

(5) The above embodiment describes a case in which multilayerinterference filters are used as color filters, although, needless tosay, the present invention is not limited as such. Alternatively,single-layer filters may be used.

FIG. 12 is a cross-sectional view showing a portion of a structure of asolid-state imaging device according to variation 5. As shown in FIG.12, a solid-state imaging device 10 includes a semiconductor substrate1001, photoelectric converters 1002, a planarizing layer 1003, a lightshielding film 1004, a planarizing layer 1005 and condenser lenses 1006.The light shielding film 1004 has apertures 1004 a in which single-layerfilters 1007 r, 1007 g and 1007 b are disposed.

The condenser lenses 1006 focus incident light onto correspondingphotoelectric converters 1002. The multilayer interference filters 1007r, 1007 g and 1007 b selectively transmit only specific wavelengthcomponents of the incident light. The light shielding film 1004 preventslight transmitted by the condenser lenses 1006 from being incident onnon-corresponding photoelectric converters 1002.

Each of the photoelectric converters 1002 outputs an electrical signalaccording to a quantity of incident light. The planarizing layer 1003 iscomposed of monosilicon dioxide and provides a flat upper surface forformation of the single-layer filters 1007 r, 1007 g and 1007 b. Theplanarizing layer 1005 provides a flat upper surface for arrangement ofthe condenser lens 1006.

Here, the single-layer filters 1007 r, 1007 g and 1007 b are composed ofamorphous silicon. The single-layer filters 1007 r, 1007 g and 1007 bhave respective film thicknesses d of 70 nm, 55 nm and 40 nm. Amorphoussilicon has a refractive index n of 4.5, 4.75 and 5.0 in relation to 650nm, 530 nm and 470 nm wavelength light, whereby the following equationexpresses a relation between the wavelength λ, at which thetransmissivity of the single-layer filters is maximized, and therefractive index and film thickness of the single-layer filters.

$\frac{\lambda}{2} = {nd}$

Consequently, the single-layer filter 1007 r has spectral properties inwhich transmissivity is maximized at a wavelength of 650 nm. Thetransmissivities of the single-layer filters 1007 g and 1007 b aremaximized at wavelengths of 530 nm and 470 nm respectively.

Generally, with a medium of a given film thickness, a reinforcingwavelength and weakening wavelength are determined according to the filmthickness as a result of reflection between the film and an externalmedium, thereby generating interference. Amorphous silicon can be calledan absorbent material due to having a large extinction coefficient offrom 0 to 2 at wavelengths from 400 nm to 700 nm. Amorphous silicon thusabsorbs light in a specific wavelength region.

Consequently, given that amorphous silicon transmits light of differentwavelength regions depending on the film thickness, amorphous siliconcan be made into color filters by varying the film thickness per lightreceiving cell. It is thus possible to gain the effects of the presentinvention even if single-layer filters are used instead of multilayerinterference filters.

Although the present invention has been fully described by way ofexamples with reference to the accompanying drawings, it is to be notedthat various changes and modifications will be apparent to those skilledin the art. Therefore, unless such changes and modifications depart fromthe scope of the present invention, they should be construed as beingincluded therein.

1. A solid-state imaging device comprising: a color filter that iscomposed of an inorganic material and configured to transmit a specificwavelength component of incident light; a light shielding filmconfigured to shield incident light; and a photoelectric converterconfigured to generate an electrical signal according to a quantity oflight transmitted by the color filter, wherein the light shielding filmhas an aperture at a position opposing the photoelectric converter, thecolor filter is disposed in the aperture of the light shielding film, afilm thickness of the color filter is less than or equal to a filmthickness of the light shielding film, the color filter is a multilayerinterference filter, the multilayer interference filter is composed of apair of λ/4 multilayer films and a spacer layer sandwiched therebetween,each multilayer film being constituted from two types of alternatelylaminated dielectric layers that are of different materials and have asame optical thickness, and the spacer layer having a different opticalthickness from the dielectric layers constituting the λ/4 multilayerfilms, and the dielectric layers that constitute the λ/4 multilayerfilms consist of two materials selected from the group consisting ofmonosilicon dioxide, monotitanium dioxide, ditantalum pentoxide,monozirconium dioxide, monosilicon mononitride, trisilicon tetranitride,dialuminum trioxide, monomagnesium difluoride, monohafnium trioxide andmonomagnesium dioxide.
 2. The solid-state imaging device of claim 1,wherein the dielectric layers that constitute the λ/4 multilayer filmsconsist of monosilicon dioxide and monotitanium dioxide.